Background Randomized trials suggest that laparoscopic cholecystectomy should be performed on first admission for acute cholecystitis. However, this is not widely practiced, possibly because of a perceived high conversion rate. We hypothesized that delay from onset of symptoms may increase the conversion rate. Methods We performed a retrospective case note review of patients undergoing emergency cholecystectomy in a single institution between January 2002 and December 2005. We analyzed whether delay from onset of symptoms was related to the conversion rate in patients with a histopathological diagnosis of acute cholecystitis. Results Of patients who underwent emergency laparoscopic cholecystectomy in our institution, 32.4% (197/608) had acute cholecystitis on histopathology. The conversion rate of those with acute cholecystitis was considerably higher (24.4%) than for those with other pathologies (6.3%). For patients with acute cholecystitis, the conversion rates increased with duration of symptoms: 9.5%, 16.1%, 38.9%, and 38.6% for delays of 0-2 days, 3-4 days, 5-6 days, and > 6 days from symptom onset, respectively (chi-square for trend = 14.27, DF = 1, p = 0.00016). Most conversions were due to the presence of acute inflammatory adhesions. Conclusions Early intervention for acute cholecystitis (preferably within 2 days of onset of symptoms) is most likely to result in successful laparoscopic cholecystectomy; increasing delay is associated with conversion to open surgery.The abstract was presented at